Reactor effluents from polymerization processes comprising, for example, polypropylene can contain polymer particles, dissolved amorphous polymer, catalyst residues, and diluent, e.g. liquid propylene, and liquid polymer. It is frequently necessary to remove one or more of these materials, e.g. soluble polymer from the desired product, e.g. the crystalline polymer, in order to obtain a product having acceptable physical properties, e.g. stiffness, tensile strength, etc. In addition, catalyst residues often must be substantially removed to minimize corrosion of subsequent processing equipment, e.g. extruders, to minimize discoloration of the finished polymer and to reduce the quantity of stabilizer package required to protect the finished polymer from the deleterious effects of heat, oxygen and UV light.
Polymerization reactor effluents comprising PPS, for example, can contain polymer particles, unreacted p-dichlorobenzene, N-methyl-2-pyrrolidone (NMP) solvent and salt (NaCl). Roughly the same amount of salt and polymer is made in this process. It is necessary to wash as much salt as possible from the polymer as well as other ash-forming by-products in order to obtain a commercially acceptable product. Generally, before this is done, the NMP and p-dichlorobenzene are removed by flashing and the product is slurried in water, filtered, reslurried, etc. to remove the salt.